It has been found that pressurized air can be fractionalized by removing various elements therefrom through the use of molecular sieves. Molecular sieve separators such as disclosed in U.S. Pat. Nos. 2,944,627, 3,280,536 and 3,142,547 disclose the use of molecular sieve materials having an Angstrom pore size of approximately 5 and which are capable of producing an oxygen enriched product fluid from pressurized air. In such separators it is the usual practice to employ several beds of molecular sieve material. While one bed is being desorbed another bed, through the operation of control valves, is sequentially presented with a source of pressurized air to establish a continuous supply of the oxygen enriched product fluid.
In beds of adsorption material disclosed in the prior art which have substantially the same cylindrical configuration, it has been found that the particles of adsorption material closest to the entrance port through which pressurized air is presented, adsorb the majority of nitrogen in the production of the oxygen enriched product fluid. Thus, the particles of adsorption material adjacent the exit port are not effectively utilized in the production of the oxygen enriched product fluid.
In addition, it was discovered that the efficiency of such molecular sieve separators is also dependent upon temperature. From experimentation it has been determined that the most effective of separation occurs when both the pressurized air and beds of adsorption material are maintained at a temperature of about 80.degree. F. Unfortunately, when molecular sieve separators are used in aircraft the temperature in unpressurized aircraft cabins can reach -65.degree. F. at altitudes approaching 30,000 feet. Under these conditions, thereafter the efficiency of such prior art molecular separators is greatly reduced and the production of the oxygen enriched product fluid in such aircraft is essentially eliminated at an altitude when a pilot needs oxygen the most.